Physics 202, Lecture 16 Today’s Topics Reminder of Lenz’s and Faraday’s Laws Motional EMF Electric Generators Reminder: Midterm 2, Nov 2, 5:30-7:00pm Exam 2 Reminder Exam time: Wednesday, November 2, 5:30-7PM Covering: Chapters 25-28 (Section 28.1-28.5), lecture material, lab material (E4,E6), and homework. About 20 Multiple Choice Questions Bring: Pen/pencil Calculator (no programming functionality!) 1 single-sided formula sheet, self-prepared -- no photocopying! Exam room assignment, special arrangements, other logistics, etc will be spelled out in a forthcoming email. A practice exam will be sent to you by email this week. Lenz’s Law (Reminder) The emf due to change of magnetic flux tends to create a current which produces a magnetic field to compensate the change of original magnetic flux. Note: Real current may or may not generated. Lenz’s law is a convenient way to determine the direction of the emf due to magnetic flux change. Review: Lenz’s Law Lenz’s law in plain words: the induced emf always tend to work against the original cause of flux change Cause of dΦ B /dt “Current” due to Induced ε will: Increasing B generate B in opposite dir. Decreasing B generate B in same dir. Relative motion subject to a force in opposite direction of relative motions Note: “Current” may not actually produced if no circuit Quizzes/Exercises: Determine Direction Of emf Indicate the direction of emf in the following cases: + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |B| increases + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + |B| decreases |B| decreases |B| increases |B| decreases path outside B or Demo: Jumping Ring and more conducting ring v switch on and the ring jumps
3
Embed
Exam 2 Reminder - UW-Madison Department of Physics 202, Lecture 16 Today’s Topics Reminder of Lenz’s and Faraday’s Laws Motional EMF Electric Generators Reminder: Midterm 2,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Physics 202, Lecture 16Today’s Topics
Reminder of Lenz’s and Faraday’s Laws
Motional EMF
Electric Generators
Reminder: Midterm 2, Nov 2, 5:30-7:00pm
Exam 2 Reminder
Exam time: Wednesday, November 2, 5:30-7PMCovering: Chapters 25-28 (Section 28.1-28.5), lecturematerial, lab material (E4,E6), and homework.
About 20 Multiple Choice Questions
Bring: Pen/pencil Calculator (no programming functionality!)
1 single-sided formula sheet, self-prepared --no photocopying!
Exam room assignment, special arrangements, otherlogistics, etc will be spelled out in a forthcoming email.A practice exam will be sent to you by email this week.
Lenz’s Law (Reminder) The emf due to change of magnetic flux tends to
create a current which produces a magnetic field tocompensate the change of original magnetic flux. Note: Real current may or may not generated. Lenz’s law is a convenient way to determine the
direction of the emf due to magnetic flux change.
Review: Lenz’s Law Lenz’s law in plain words: the induced emf always tend
to work against the original cause of flux change
Cause of dΦB/dt “Current” due to Induced ε will:Increasing B generate B in opposite dir.Decreasing B generate B in same dir.
Relative motion subject to a force in oppositedirection of relative motions
Note: “Current” may not actually produced if no circuit
Quizzes/Exercises: Determine Direction Of emf
Indicate the direction of emf in the following cases:+ + + + + + + + ++ + + + + + + + ++ + + + + + + + ++ + + + + + + + ++ + + + + + + + ++ + + + + + + + +|B| increases